Developmental Synaptic Changes Increase the Range of Integrative Capabilities of an Identified Excitatory Neocortical Connection

J Neurosci. 1999 Mar 1;19(5):1566-76. doi: 10.1523/JNEUROSCI.19-05-01566.1999.

Abstract

Excitatory synaptic transmission between pyramidal cells and fast-spiking (FS) interneurons of layer V of the motor cortex was investigated in acute slices by using paired recordings at 30 degrees C combined with morphological analysis. The presynaptic and postsynaptic properties at these identified central synapses were compared between 3- and 5-week-old rats. At these two postnatal developmental stages, unitary EPSCs were mediated by the activation of AMPA receptors with fast kinetics at a holding potential of -72 mV. The amplitude distribution analysis of the EPSCs indicates that, at both stages, pyramidal-FS connections consisted of multiple functional release sites. The apparent quantal size obtained by decreasing the external calcium ([Ca2+]e) varied from 11 to 29 pA near resting membrane potential. In young rats, pairs of presynaptic action potentials elicited unitary synaptic responses that displayed paired-pulse depression at all tested frequencies. In older animals, inputs from different pyramidal cells onto the same FS interneuron had different paired-pulse response characteristics and, at most of these connections, a switch from depression to facilitation occurred when decreasing the rate of presynaptic stimulation. The balance between facilitation and depression endows pyramidal-FS connections from 5-week-old animals with wide integrative capabilities and confers unique functional properties to each synapse.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aging
  • Animals
  • Electric Stimulation
  • Excitatory Amino Acid Antagonists / pharmacology
  • Excitatory Postsynaptic Potentials / drug effects
  • Excitatory Postsynaptic Potentials / physiology
  • In Vitro Techniques
  • Interneurons / physiology
  • Motor Cortex / growth & development
  • Motor Cortex / physiology
  • Neocortex / physiology*
  • Patch-Clamp Techniques
  • Pyramidal Cells / physiology
  • Quinoxalines / pharmacology
  • Rats
  • Rats, Wistar
  • Receptors, AMPA / physiology
  • Synapses / physiology*
  • Synaptic Transmission / drug effects
  • Synaptic Transmission / physiology

Substances

  • Excitatory Amino Acid Antagonists
  • Quinoxalines
  • Receptors, AMPA
  • 2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline
  • FG 9041